Preparation of 1,6,8-decatriene

ABSTRACT

A method for preparing 1,6,8-decatriene by contacting 1,4,9decatriene, in the vapor phase and in the absence of oxygen, with an alumina catalyst. Preferred catalysts are promoted with an alkali metal salt.

United States Patent 1191 Koch 1451 Apr. 10, 1973 PREPARATION OF 1,6,8-DECATRIENE 3,376,358 4/1968 Schneider ..260/677 R 3,546,312 12/1970 Heckelsberg et al. ....260/683 R [75 1 Invent gf' wflmmgmn 3,449,463 6/1969 Kenton et a1 ..260/677 6 3,546,310 12/1970 Cardenas ..260/677 73 As' :E.I.dPntdN dC 1 my, s g 33? an FOREIGN PATENTS OR APPLICATIONS 22 Filed: May 5 1972 1,226,095 10/1966 Germany ..260/677 1,443,465 11/1968 Germany ..260/677 [21] Appl. No.: 250,498

Primary Examiner--Delbert E. Gantz 52 US. Cl. ..260/677 R, 260/6832 Assistant Examiner-1MB 51 rm. c1 ..C07c 5/22 Ammey-Alamn Bowen, [58] Field of Search ..260/677, 680 R, 666 B,

260/6832 ABSTRACT A method for preparing 1,6,8-decatriene by contact- [56] References C'ted ing 1,4,9-decatriene, in the vapor phase and in the UNITED STATES PATENTS absence of oxygen, with an alumina catalyst. Preferred catalysts are promoted with an alkali metal salt. 3,579,606 5/1971 Umbach ..260/677 3,376,359 4/1968 Schneider ..260/677 R 8 Claims, N0 Drawings PREPARATION OF 1,6,8-DECATRIENE BACKGROUND OF THE INVENTION This invention pertainsto the selective isomerization of 1,4,9-decatriene to 1,6,8-decatriene.

Amorphous dipolymers of ethylene and propylene are well known in the art to possess elastomeric properties. These dipolymers will undergo peroxide curing but are limited in that they will not undergo other types of curing, such as sulfur curing which is preferred by the rubber industry.

The art has overcome this problem by copolymerizing a polyunsaturated monomer, such as a diene or triene, with ethylene and propylene. Preferred polyunsaturated monomers have a double bond which readily copolymerizes with ethylene and propylene, and at least one double bond which does not enter the polymerization reaction. Resulting copolymers have saturated backbones with pendant unsaturation available as curing sites.

The compound 1,4,9-decatriene has been suggested as a useful third monomer in preparing sulfur-vulcanizable copolymers of ethylene and propylene. This compound has two terminal double bonds, both of which copolymerize with ethylene and propylene. The resulting polymer has a gel content higher than desired, making processing difficult, and has fewer cure sites than if only one double bond entered the copolymerization reaction.

Selection of 1,6,8-dcatriene as a third monomer in ethylene-propylene copolymerization avoids the disadvantage posed by l,4,9-decatriene, its isomer. The compound 1,6,8-decatriene has one terminal bond which enters the copolymerization reaction and two internal double bonds which are not copolymerized. The latter double bonds are available as copolymer curing sites.

SUMMARY OF THE INVENTION In accordance with this invention 1,4,9-decatriene is selectively isomerized to 1,6,8-decatriene by contact, in the vapor phase and in the absence of oxygen, with an alumina catalyst. The preferred catalyst is a nonacidic or alkali metal salt promoted alumina.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The compound 1,4,9-decatriene, which is selectively isomerized by the process of this invention, is conveniently prepared by reacting butadiene, or an alkyl substituted butadiene such as isoprene, with ethylene using the process of U.S. Pat. Nos. 3,376,358 or 3,376,359. It is understood that the term 1,4,9- decatriene, as used herein, includes alkyl substituted 1,4,9-decatriene such as dimethyl-l,4,9-decatriene which is formed when isoprene is the selected starting material.

In practicing this invention l,4,9-decatriene is contacted, in the vapor phase, with an alumina catalyst. The starting compound 1,4,9-decatriene is a liquid at ambient temperatures and is conveniently vaporized in a separate chamber shortly prior to the isomerization reaction.

lsomerization is conducted in a flow reactor containing the alumina catalyst. Prior to the introduction of 1,4,9-decatriene the reaction vessel is purged with a non-reactive gas, such as nitrogen, to remove oxygen. Oxygen is excluded during the course of the isomerization reaction. Conveniently, isomerization is conducted at atmospheric pressure in the presence of a non-reactive diluent such as nitrogen. Higher or lower pressures can be selected, however, and use of a non-reactive diluent is not essential.

The reaction is conducted at a temperature above about 175C. to maintain 1,4,9-decatriene and the 1,6,8-decatriene isomerization product in the vapor phase. The reaction is generally conducted at a temperature lower than 300C. since competing cracking reactions reduce yields at higher temperatures. A preferred temperature range is about 200 to 250C., with lower temperatures within this range being especially perferred. Temperatures of about 200C. will give especially good conversion rates with low catalyst deterioration.

While any alumina may be selected as the isomerization catalyst, commercial alumina is generally acidic and produces lower yields than non-acidic alumina, or alumina promoted with sodium, potassium, lithium, or cesium salts. The preferred alkali metal salt promoted alumina catalysts will contain less than about 1 percent, and preferably about 0.2 to 0.5 percent, by weight of promoter. Promoted catalysts preferred in practicing this invention are prepared using standard techniques. For example, the alumina can be coated with the promoter in carbonate, bicarbonate, or hydroxide solution followed by drying.

Conversions of about 58 percent, with 96 percent yield, have been obtained in isomerizing 1,4,9- decatriene to 1,6,8-decatriene using the preferred promoted alumina catalysts.

The l,6,8-decatriene is useful as a comonomer in the copolymerization of ethylene and propylene. This triene has internal conjugated unsaturation which does not enter copolymerization. Resulting ethylene/propylene/ l ,6,8-decatriene terpolymers have pendant conjugated unsaturation available for sulfur, Diels-alder, or resin curing.

In the examples that follow all percentages are proportional to weight unless otherwise indicated.

EXAMPLE I Preparation of 1,6,8-Decatriene using Alumina Catalysts A. lsomerization Apparatus The isomerization apparatus consists of a 25 mm. o.d. glass tube mounted vertically and defined into two sections by 8-inch tube furnaces. The tube in the upper furnace is used as a preheater, and the tube in the lower furnace contains the catalyst. The tube in the preheater is packed with quartz or silicon carbide chips to ensure vaporization of the feed material. B. Preparation of 1,6,8-Decatriene Twenty cc. of the catalysts listed in Table l are placed in the reaction furnace of the previously described apparatus in individual runs. The reaction temperature is [75C. Thirty cc. of 1,4,9-decatriene per hour is fed to the isomerization apparatus and the effluent analyzed at various times by gas chromatography on a 10 percent SE 30 (silicon oil) on -80 distillation and its structure verified by infrared and 5 Tremd Alumina nuclear magnetic resonance spectroscopy.

TABLE 1 Time from 1,4,9- 1,6,8- Octa- Type of beginning Deca- Deca- Unknown octa- Alumina of Run triene triene diene Grace eta 210 51 49 490 73 27 Kaiser XA-757 195 49 44 7 555 68 31 1 Kaiser ILA-161 30 35 63 2 285 42 45 8 powder form, 95% eta alumina, 5% gamma alumina ball form, low sodium (0.02% Na o) alumina essentially the same as Kaiser XA-757 The above table shows that conversion decreases with time when using an untreated alumina catalyst.

EXAMPLE II TABLE ll Time from 1,4,9- 1,6,8- Feed beginning Deca- Deca- Rate of Run triene triene (Ll-IVS) 330 min. 36 56 1.5 Kaiser KA-302 720 min. 38 62 1.5

2 days 37 63 1.5

8 days 42 58 1.5 Untreated Alumina 450 min. 44 56 2 Kaiser KA-302 600 min. 57 43 l Ball form; 93.6% A1, 6.0% loss on ignition, balance SiO,, Fe o TiO,, and Na,0; 380 sq. meters per gram.

Liquid hourly space velocity, pounds as liquid per hour.

8% material of unknown structure.

The table of Example 11 shows that promoted catalyst gives continuing good conversions after 8 days, whereas conversion achieved with unpromoted catalyst had significantly decreased after 10 hours.

I claim:

1. A method for preparing 1,6,8-decatriene consist ing essentially of contacting 1,4,9-decatriene, in the vapor phase and in the absence of oxygen, with an alumina catalyst.

2. The method of claim 1 wherein the alumina catalyst is a non-acidic alumina.

3. The method of claim 1 wherein the alumina catalyst is promoted with at least one alkali metal salt.

4. The method of claim 3 wherein the temperature is at least C.

5. The method of claim 4 wherein the temperature is about 200 to 250C.

6. The method of claim 5 wherein the promoter is present in an amount up to about 1 percent by weight of the alumina.

7. The method of claim 6 wherein the promoter is present in the amount of about 0.2 to 0.5 percent by weight of the alumina.

8. The method of claim 7 wherein the promoter is a sodium salt. 

2. The method of claim 1 wherein the alumina catalyst is a non-acidic alumina.
 3. The method of claim 1 wherein the alumina catalyst is promoted with at least one alkali metal salt.
 4. The method of claim 3 wherein the temperature is at least 175*C.
 5. The method of claim 4 wherein the temperature is about 200* to 250*C.
 6. The method of claim 5 wherein the promoter is present in an amount up to about 1 percent by weight of the alumina.
 7. The method of claim 6 wherein the promoter is present in the amount of about 0.2 to 0.5 percent by weight of the alumina.
 8. The method of claim 7 wherein the promoter is a sodium salt. 